Rushden struggled to defeat nine man Wycombe Wanderers thanks to goals from Rodney Jack and Onandi Lowe.
The visitors made the worst possible start in the fifth minute when goalkeeper Frank Talia was adjudged to have committed a professional foul on Lowe outside the penalty area and was shown the red card.
Even with an extra man, Diamonds found it difficult to capitalise on the 10 men.
On nine minutes Diamonds' keeper Billy Turley dropped a free kick from Chris Vinnicombe while at the other end, Lowe beat two players before seeing his left foot shot drift into the side netting.
On 13 minutes, Diamonds suffered a blow when defender Marcus Bignot had to leave the field with a repeat of his hamstring injury.
A minute later Jack saw his header flash wide before Wycombe got into their stride and enjoyed more of the play.
With little goalmouth action at either end, it was not until the 28th minute that Wycombe's stand-in goalkeeper Richard Harris was called into action. Firstly, Lowe beat two defenders but saw his right foot shot go wide and then seconds later, Lowe had an even better chance but Harris stood his ground to block the shot.
On the half-hour, Vinnicombe headed a Paul Hall volley off the line before the home side took the lead on 34 minutes. Lowe combined well with Andy Burgess on the left and Stuart Gray's low shot was only parried by Harris, allowing Jack to toe-poke the ball home.
Immediately after the goal, Wanderers manager Lawrie Sanchenz was sent to the stands for descent.
Diamonds almost increased their lead eight minutes before the interval when Gray saw a 25 yard shot come back off the bar.
In the second half, Wycombe enjoyed the better of the chances. On 51 minutes Jermaine McSporran should have done better after capitalising on Andrew Sambrook's mistake, while on 69 minutes Roger Johnson missed the target with a free header.
Diamonds made the game safe six minutes from time. Vinnicombe was sent off for a second bookable offence after Duane Darby had been fouled and from the resulting free kick on the edge of the penalty area, Lowe buried his shot past the despairing Steve Brown, Wycombe's third goalkeeper of the afternoon.